Engine stop-and-start systems, such as idle reduction control systems, have been recently developed. Such engine stop-and-start systems are designed to automatically stop an internal combustion engine of a vehicle in response to detecting a driver's engine stop operation, such as the operation of a brake pedal. These engine stop-and-start systems are also designed to restart the internal combustion engine in response to detecting a driver's operation to start the vehicle, such as the operation of an accelerator pedal. These engine stop-and-start systems aim at reducing fuel cost, exhaust emission, and the like.
In view of improvement of, for example, drivability, these engine stop-and-start systems are required to restart an internal combustion engine in immediate response to the occurrence of an engine restart request. Various technical approaches to achieve such a requirement have been proposed.
Japanese Examined Patent Publication No. 4211208 discloses a technical approach included in these various technical approaches. The technical approach disclosed in the Patent Publication is designed to, when an engine restart request occurs during the rotational speed of a crankshaft of an internal combustion engine (referred to as an engine) dropping, cause a starter to crank the engine without waiting the complete stop of rotation of the engine (crankshaft).
Specifically, the technical approach is designed to, when an engine restart request occurs during the rotational speed of the crankshaft of the engine dropping after automatic stop of the engine, rotate a pinion so that the rotational speed of the pinion is controlled to reach the rotational speed of a ring gear (engine) coupled to the output shaft of the engine. When the rotational speed of the pinion is synchronized with that of the ring gear, the technical approach engages the rotating pinion with the ring gear to thereby return the engine into operational status in immediate response to the occurrence of an engine restart request.